Plasma processing system

ABSTRACT

There is provided a plasma processing system capable of making a processing rate uniform without the occurrence of charge-up damage and arcing damage when a substrate to be processed is plasma-processed. The plasma processing system comprises:  
     a chamber ( 1 ) capable of being held in vacuum;  
     a pair of electrodes which face each other in the chamber, the pair of electrodes comprising a first electrode ( 2 ) for supporting thereon a substrate (W) to be processed, and a second electrode ( 16 ) facing the first electrode;  
     electric field forming means ( 10 ) for forming a high-frequency field having a predetermined power density between the pair of electrodes;  
     process gas supply means ( 15 ) for supplying a process gas into the chamber;  
     magnetic field forming means ( 21 ), provided around the chamber, for forming a magnetic field around a processing space which is formed between the pair of electrodes; and  
     a conductive or insulating focus ring ( 5 ) which is provided around the substrate on the first electrode,  
     wherein the ratio of the outer diameter of the focus ring to the diameter of the substrate is set to be in the range of from about 1.3 to about 1.4.

BACKGROUND OF THE INVENTION

[0001] 1. Field of The Invention

[0002] The present invention relates generally to a plasma processing system for processing a substrate, such as a semiconductor wafer, with plasma.

[0003] 2. Description of Related Background Art

[0004] In recent years, a magnetron plasma etching system for producing a high-density plasma in a relatively low pressure atmosphere to carry out a fine pattern etching has been put to practical use. This system is designed to horizontally apply a magnetic field, which leaks out of a permanent magnet arranged above a chamber, to a semiconductor wafer (which will be hereinafter simply referred to as a wafer) and to apply a high-frequency field perpendicular thereto, to generate electrons to utilize the drift motion of the electrons to etch the wafer.

[0005] In such a magnetron plasma, the magnetic field perpendicular to the electric field, i.e., the horizontal magnetic field parallel to the wafer, contributes to the drift motion of electrons. However, since the horizontal magnetic field formed by the above described system is not always uniform, the uniformity of plasma is not sufficient, so that there are problems in that the ununiformity of etch rate and charge-up damage are caused.

[0006] When a process evaluation in a plasma processing is carried out, the degree of charging damage due to plasma is generally evacuated as described in, e.g., “Electronic Engineering (the January number, 1998, pages 72-76)”.

[0007] In the plasma etching system, the etch rate is required to be uniform on the whole of a silicon wafer. However, if the above described conventional system is used, the wafer inplane ununiformity of an etching processing is caused by the following. That is, electrons move in a direction perpendicular to the magnetic field by the cycloid motion of electrons, so that the electron density is very high in a part of the outer peripheral portion of the wafer to damage the wafer. Ions in plasma collide with the surface of the wafer by the action of ion sheath generated between a second electrode and a first electrode. At this time, part of the ions colliding with the surface of the wafer are injected into the wafer to damage the wafer. If the electron density in plasma is high, the number of ions injected into the wafer is high, so that the damage is great. Since the magnetron etching system rotates the magnetic field, the damaged portion is the whole area of the outer peripheral portion of the wafer.

[0008] On the other hand, it has been proposed that a focus ring substantially having the same potential as that of a first electrode on which an object to be processed is mounted is provided, and the outer diameter of the focus ring is formed so as to be greater than the diameter of the object to substantially extend the apparent area of the object (Japanese Patent Laid-Open No. 5-335283).

[0009] However, in the above described conventional proposal, the outer diameter of the focus ring is only greater than the diameter of the object, and the same focus ring is also used in principle with respect to an object to be processed, which has a different diameter, so that there is no idea that the outer diameter of the focus ring is set so as to vary in accordance with the diameter of the object.

SUMMARY OF THE INVENTION

[0010] It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a plasma processing system capable of carrying out a uniform plasma processing in the plane of an object to be processed.

[0011] In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, a plasma processing system comprises:

[0012] a chamber capable of being held in vacuum;

[0013] a pair of electrodes which face each other in the chamber, the pair of electrodes comprising a first electrode for supporting thereon a substrate to be processed, and a second electrode facing the first electrode;

[0014] electric field forming means for forming a high-frequency field having a predetermined power density between the pair of electrodes;

[0015] process gas supply means for supplying a process gas into the chamber;

[0016] magnetic field forming means, provided around the chamber, for forming a magnetic field around a processing space which is formed between the pair of electrodes; and

[0017] a conductive or insulating focus ring which is provided around the substrate on the first electrode,

[0018] wherein the ratio of the outer diameter of the focus ring to the diameter of the substrate is set to be in the range of from about 1.3 to about 1.4.

[0019] The outer diameter of the focus ring may be set to be in the range of from 275 mm to 280 mm when the diameter of the substrate is 203 mm (8 inches) if the power density of the high-frequency field applied to the substrate is in the range of from 2.8 W/cm² to 3.9 W/cm².

[0020] The outer diameter of the focus ring may be set to be greater than 275 mm and not greater than 280 mm when the diameter of the substrate is 203 mm (8 inches) if the power density of the high-frequency field applied to the substrate is in the range of from 2.8 W/cm² to 3.9 W/cm².

[0021] The outer diameter of the focus ring may be set to be in the range of from 275 mm to 280 mm when the diameter of the substrate is 203 mm (8 inches) if the power density of the high-frequency field applied to the substrate is not less than 2.8 W/cm² and less than 3.9 W/cm².

[0022] The outer diameter of the focus ring may be set to be in the range of from 412 mm to 420 mm when the diameter of the substrate is 305 mm (12 inches) if the power density of the high-frequency field applied to the substrate is in the range of from 2.8 W/cm² to 3.9 W/cm².

[0023] The outer diameter of the focus ring may be set to be greater than 412 mm and not greater than 420 mm when the diameter of the substrate is 305 mm (12 inches) if the power density of the high-frequency field applied to the substrate is in the range of from 2.8 W/cm² to 3.9 W/cm².

[0024] The outer diameter of the focus ring may be set to be in the range of from 412 mm to 420 mm when the diameter of the substrate is 305 mm (12 inches) if the power density of the high-frequency field applied to the substrate is not less than 2.8 W/cm² and less than 3.9 W/cm².

[0025] The outer diameter of the focus ring may be set to be in the range of from 275 mm to 280 mm when the diameter of the substrate is 203 mm (8 inches), and in the range of from 412 mm to 420 mm when the diameter of the substrate is 305 mm (12 inches), if the power density of the high-frequency field applied to the substrate is 2.8 W/cm².

[0026] The outer diameter of the focus ring may be set to be greater than 275 mm and not greater than 280 mm when the diameter of the substrate is 203 mm (8 inches), and may be set to be greater than 412 mm and not greater than 420 mm when the diameter of the substrate is 305 mm (12 inches), if the power density of the high-frequency field applied to the substrate is 3.9 W/cm².

[0027] According to the present invention, it is possible to avoid the occurrence of charge-up damage or arcing damage since the ratio of the outer diameter of the focus ring to the diameter of the substrate is set to be in the range of from about 1.3 to about 1.4.

[0028] If the power density of the high-frequency field applied to the substrate is in the range of from 2.8 W/cm² to 3.9 W/cm², the outer diameter of the focus ring is set to be in the range of from 275 mm to 280 mm when the diameter of the substrate is 203 mm (8 inches), and the outer diameter of the focus ring is set to be in the range of from 412 mm to 420 mm when the diameter of the substrate is 305 mm (12 inches), so that it is possible to avoid the occurrence of charge-up damage or arcing damage without identifying whether damage is charge-up damage or aching damage with respect to a substrate having a diameter of 8 inches or 12 inches.

[0029] If the power density of the high-frequency field applied to the substrate is in the range of from 2.8 W/cm² to 3.9 W/cm², the outer diameter of the focus ring is set to be greater than 275 mm and not greater than 280 mm when the diameter of the substrate is 203 mm (8 inches), and the outer diameter of the focus ring is set to be greater than 412 mm and not greater than 420 mm when the diameter of the substrate is 305 mm (12 inches), so that it is possible to avoid the occurrence of charge-up damage regardless of the presence of occurrence of aching damage with respect to a substrate having a diameter of 8 inches or 12 inches.

[0030] If the power density of the high-frequency field applied to the substrate is not less than 2.8 W/cm² and less than 3.9 W/cm², the outer diameter of the focus ring is set to be in the range of from 275 mm to 280 mm when the diameter of the substrate is 203 mm (8 inches), and the outer diameter of the focus ring is set to be in the range of from 412 mm to 420 mm when the diameter of the substrate is 305 mm (12 inches), so that it is possible to avoid the occurrence of charge-up damage and arcing damage with respect to a substrate having a diameter of 8 inches or 12 inches.

[0031] If the power density of the high-frequency field applied to the substrate is set to be 2.8 W/cm² by the request of the conditions in the plasma processing, the outer diameter of the focus ring is set to be in the range of from 275 mm to 280 mm when the diameter of the substrate is 203 mm (8 inches), and in the range of from 412 mm to 420 mm when the diameter of the substrate is 305 mm (12 inches), so that it is possible to avoid the occurrence of charge-up damage and arcing damage.

[0032] If the power density of the high-frequency field applied to the substrate is set to be 3.9 W/cm² by the request of the conditions in the plasma processing, the outer diameter of the focus ring is set to be greater than 275 mm and not greater than 280 mm when the diameter of the substrate is 203 mm (8 inches), and is set to be greater than 412 mm and not greater than 420 mm when the diameter of the substrate is 305 mm (12 inches), so that it is possible to avoid the occurrence of charge-up damage and arcing damage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiments of the invention. However, the drawings are not intended to imply limitation of the invention to a specific embodiment, but are for explanation and understanding only.

[0034] In the drawings:

[0035]FIG. 1 is a sectional view showing a preferred embodiment of a plasma etching system according to the present invention;

[0036]FIG. 2 is a horizontal sectional view schematically showing a ring magnet which is arranged around a chamber of the system of FIG. 1;

[0037]FIG. 3 is a graph showing the relationship between the outer diameter of a focus ring 5 and a non-defective rate (%) based on the presence of occurrence of charge-up damage, when the diameter of a wafer is 8 inches;

[0038]FIG. 4 is a table showing the relationship between the outer diameter of a focus ring and the presence of occurrence of arcing damage when the diameter of a wafer is 8 inches, wherein (a) shows a case where the power density of a high-frequency field is 2.8 W/cm² and (b) shows a case where the power density of a high-frequency field is 3.9 W/cm².

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Referring now to the accompanying drawings, the preferred embodiment of the present invention will be described below.

[0040]FIG. 1 is a sectional view showing a preferred embodiment of a plasma etching system according to the present invention. This etching system has an airtight stepped cylindrical chamber 1 which comprises a small-diameter upper portion 1 a and a large-diameter lower portion 1 b and which has a wall portion of, e.g., aluminum.

[0041] In this chamber 1, a supporting table 2 for horizontally supporting thereon a wafer W serving as a substrate to be processed is provided. The supporting table 2 is formed of, e.g., aluminum, and is supported on a supporting table 4 of a conductor via an insulating plate 3. On the outer periphery of the upper portion of the supporting table 2, a focus ring 5 of a conductive material or an insulating material is provided. The supporting table 2 and the supporting table 4 are vertically movable by means of a ball screw mechanism including a ball screw 7. The driving portion below the supporting table 4 is covered with a bellow 8 of a stainless steel (SUS). The chamber 1 is grounded. A refrigerant passage (not shown) is provided in the supporting table 2 to be able to cool the supporting table 2. Outside of the bellow 8, a bellow cover 9 is provided.

[0042] A feeder 12 for supplying a high frequency power is connected to the supporting table 2 substantially at the center thereof. The feeder 12 is connected to a matching box 11 and a high frequency power supply 10. From the high frequency power supply 10, a high frequency power of 13.56 to 150 MHz, preferably 13.56 to 67.8 MH, e.g., 40 MHz, is supplied to the supporting table 2. On the other hand, a shower head 16, which will be described later, is provided above the supporting table 2 so as to face the supporting table 2 in parallel thereto. This shower head 16 is grounded. Therefore, the supporting table 2 functions as a first electrode, and the shower head 16 functions as a second electrode, so that the supporting table 2 and the shower head 16 function as a pair of electrodes.

[0043] On the surface of the supporting table 2, an electrostatic chuck 6 for electrostatic-absorbing a wafer W is provided. The electrostatic chuck 6 comprises an electrode 6 a which is provided between insulating materials 6 b. The electrode 6 a is connected to a dc power supply 13. If a voltage is applied to the electrode 6 a from a power supply 13, the semiconductor wafer W is absorbed by, e.g., Coulomb force.

[0044] In the supporting table 2, a refrigerant passage (not shown) is formed. By circulating a suitable refrigerant therein, the temperature of the wafer W can be controlled to a predetermined temperature. In order to efficiently transmit cold from the refrigerant to the wafer W, a gas feed mechanism (not shown) for supplying He gas to the reverse of the wafer W is provided. Moreover, outside of the focus ring 5, a baffle plate 14 is provided. The baffle plate 14 is conducted to the chamber 1 via the supporting table 4 and the below 8.

[0045] The above described shower head 16 is provided on the ceiling wall of the chamber 1 so as to face the supporting table 2. The shower head 16 is provided with a large number of gas discharge holes 18 in its bottom face, and has a gas feed portion 16 a in its upper portion. In the shower head 16, a space 17 is formed. The gas feed portion 16 a is connected to a gas supply pipe 15 a, and the other end of the gas supply pipe 15 a is connected to a process gas supply system 15 for supplying a process gas of a reaction gas and a diluted gas for etching. The reaction gas may be a halogen gas, and the diluted gas may be a gas usually used in this field, such as Ar gas or He gas.

[0046] Such a process gas is supplied from the process gas supply system 15 to pass through the gas supply pipe 15 a and the gas feed portion 16 a to reach the space 17 of the shower head 16 to be discharged from the gas discharge holes 18 to be used for etching a film which is formed on the water W.

[0047] In the side wall of the lower portion 1 b of the chamber 1, an exhaust port 19 is formed. This exhaust port 19 is connected to an exhaust system 20. By operating a vacuum pump which is provided in the exhaust system 20, the interior of the chamber 1 can be pressure-reduced to a predetermined degree of vacuum. On the other hand, on the upper side of the side wall of the lower portion 1 b of the chamber 1, a gate valve 24 for opening and closing an opening for carrying the wafer W in and out is provided.

[0048] On the other hand, a ring magnet 21 is concentrically arranged around the upper portion 1 a of the chamber 1 to form a magnetic field around a processing space between the supporting table 2 and the shower head 16. As shown in FIG. 2, the ring magnet 21 comprises a plurality of anisotropic segment prismatic magnets 22 which are arranged outside of the chamber 1 in the form of a ring. The magnetizing directions of the plurality of segment prismatic magnets 22 are shifted little by little to form a uniform horizontal magnetic field B as a whole. Furthermore, FIG. 2 is a plan view of the system viewed from the top, wherein N denotes the base end side of the magnetizing direction, and S denotes the tip end side thereof, E and W denoting the positions of 90° from the base and tip end sides. This ring magnet 21 is rotatable by means of a rotating mechanism 25.

[0049] The focus ring 5 will be described below in detail.

[0050] The conductive or insulating focus ring 5 is provided around the wafer W on the supporting table 2 serving as a first electrode. Thus, the uniformity of the plasma processing can be enhanced. If the focus ring 5 is formed of a conductive material, such as silicon or SiC, a region until the focus ring functions as the first electrode, so that a plasma forming region extends above the focus ring 5 to promote the plasma processing in the peripheral portion of the wafer W to improve the uniformity of the etching rate. If the focus ring 5 of formed of an insulating material such as quartz, the giving and receiving of electric charge can not be carried out between the focus ring 5 and electrons and ions in plasma, so that the function of confining plasma can be increased to improve the uniformity of the etching rate.

[0051] The outer diameter of the focus ring 5 is set to be greater than the diameter of the wafer W, and is set so as to vary in accordance with the variation in diameter of the wafer W. For example, for reasons which will be described later, the outer diameter of the focus ring 5 is set to be in the range of from 275 mm to 280 mm when the diameter of the wafer W is 203 mm (8 inches), and is set to be in the range of from 412 mm to 420 mm when the diameter of the wafer W is 305 mm (12 inches).

[0052] Referring to FIGS. 3 and 4, the experimental grounds that the outer diameter of the focus ring 5 is set as described above will be described below. In experiments, it was examined whether charge-up damage and arcing damage occurred in the etching of the wafer W when the outer diameter of the focus ring 5 and the power density of the high-frequency field were varied. The conditions were set as follows. That is, the degree of vacuum in the chamber 1 was 20 mTorr. In addition, with respect to the flow rates of process gases supplied from the process gas supply system 15, the flow rate of C₄F₈ was 10 sccm, the flow rate of Ar was 200 sccm, the flow rate of CO was 50 sccm, and the flow rate of O₂ was 5 sccm. Moreover, the temperature of the supporting table 2 serving as the first electrode was 20° C., and the temperature of the supporting table 2 serving as the second electrode was 60° C. In addition, the voltage applied to the electrode 6 a of the electrostatic chuck 6 was 3 kV.

[0053]FIG. 3 shows the examined results of the presence of occurrence of charge-up damage when the outer diameter of the focus ring 5 was varied if the diameter of the wafer W was 8 inches. The axis of abscissas shows the outer diameter (mm) of the focus ring 5, and the axis of ordinates shows the non-defective rate (%) based on the presence of occurrence of charge-up damage. The power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power supply 10 is controlled so as to be about 2.8 W/cm². That is, the power of the supplied high-frequency field is 1500 W when the outer diameter of the focus ring 5 is 260 mm, and the power of the high-frequency field is varied every time the outer diameter of the focus ring 5 is varied so that the power density is constant to be 2.8 W/cm².

[0054] As shown in FIG. 3, when the outer diameter of the focus ring 5 is 275 mm, a non-defective rate of about 100% is obtained, and when the outer diameter of the focus ring 5 is 280 mm, a satisfied non-defective rate of about 96% is obtained. In addition, when the outer diameter of the focus ring 5 is 280 mm, the non-defective rate is slightly lower than that when it is 275 mm, but a substantially satisfied value is obtained.

[0055] In view of the foregoing, from the standpoint of the avoidance of the influence of occurrence of charge-up damage, the outer diameter of the focus ring 5 is preferably set to be in the range of from 275 mm to 280 mm when the diameter of the wafer W is 8 inches.

[0056]FIG. 4 shows the examined results of the presence of occurrence of arcing damage when the outer diameter of the focus ring 5 is varied if the diameter of the wafer W is 8 inches. The arcing damage means a phenomenon of damage due to the occurrence of a kind of creeping discharge on the surface of the wafer W. FIG. 4(a) shows a case where the power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power supply 10 is controlled to be a constant power density of about 2.8 W/cm², and FIG. 4(b) shows a case where the power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power 10 is controlled to be a constant power density of about 3.9 W/cm². In FIG. 4, the first column shows the outer diameter of the focus ring 5, the second column shows the power of the high-frequency field, and the third column shows the occurrence (NG) or non-occurrence (OK) of arcing damage.

[0057] It can be seen from FIG. 4(a) that when the power density is 2.8 W/cm², no arching damage exists if the outer diameter of the focus ring 5 is 275 mm or 280 mm. It can also be seen from FIG. 4(b) that when the power density is 3.9 W/cm², arcing damage occurs if the outer diameter of the focus ring 5 is 275 mm, and no arching damage exists if the outer diameter is 280 mm.

[0058] In view of the foregoing, from the standpoint of the avoidance of the influence of occurrence of arching damage, the outer diameter of the focus ring 5 is preferably set to be in the range of from 275 mm to 280 mm when the diameter of the wafer W is 8 inches if the power density is not less than 2.8 W/cm² and less than 3.9 W/cm². In this case, according to the results shown in FIG. 3, if the power density is not less than 2.8 W/cm² and less than 3.9 W/cm², when the diameter of the wafer W is 8 inches, it is also possible to avoid the occurrence of charge-up damage by setting the outer diameter of the focus ring 5 to be in the range of from 275 mm to 280 mm.

[0059] In addition, from the standpoint of the avoidance of the influence of charge-up damage regardless of the presence of occurrence of arcing damage, it can be said that the outer diameter of the focus ring 5 is preferably set so as to exceed 275 mm and to be 280 mm or less when the diameter of the wafer W is 8 inches if the power density is in the range of from 2.8 W/cm² to 3.9 W/cm².

[0060] From the above described results shown in FIGS. 3 and 4, the following results are led.

[0061] The outer diameter of the focus ring 5 is set to be greater than the diameter of the wafer W, and is set so as to vary in accordance with the diameter of the wafer. Specifically, the ratio of the outer diameter of the focus ring 5 to the diameter of the wafer W is preferably set to be in the range of from about 1.3 (275 mm/203 mm (8 inches) to about 1.4 (280 mm/203 mm (8 inches)).

[0062] In addition, from the standpoint of the avoidance of the influence of charge-up damage or arcing damage, it can be said that the outer diameter of the focus ring 5 is preferably set to be in the range of from 275 mm to 280 mm when the diameter of the wafer W is 8 inches if the power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power supply 10 is not less than 2.8 W/cm² and less than 3.9 W/cm².

[0063] From the standpoint of the avoidance of the influence of occurrence of charge-up damage and arcing damage, it can be said that the outer diameter of the focus ring 5 is preferably set to be in the range of from 275 mm to 280 mm when the diameter of the wafer W is 8 inches if the power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power supply 10 is not less than 2.8 W/cm² and less than 3.9 W/cm².

[0064] From the standpoint of the avoidance of the influence of occurrence of arcing-up damage regardless of the presence of occurrence of charge-up damage, it can be said that the outer diameter of the focus ring 5 is preferably set so as to exceed 275 mm and to be 280 mm or less when the diameter of the wafer W is 8 inches if the power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power supply 10 is in the range of from 2.8 W/cm² to 3.9 W/cm².

[0065] A case where the diameter of the wafer W is 12 inches will be described below. When the diameter of the wafer W was 12 inches, no experiment was carried out. However, from the results when the diameter of the wafer W is 8 inches, it can be considered as follows.

[0066] That is, it can be said that the outer diameter of the focus ring 5 is preferably set to be in the range of from 412 mm to 420 mm by doubling data (12 inches/8 inches) when the diameter of the wafer W is 8 inches, if the power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power supply 10 is not less than 2.8 W/cm² and less than 3.9 W/cm². As a result, the outer diameter of the focus ring 5 is set to be greater than the diameter of the wafer W, and is set so as to vary in accordance with the diameter of the wafer. Specifically, the ratio of the outer diameter of the focus ring 5 to the diameter of the wafer W is preferably set to be in the range of from about 1.3 to about 1.4.

[0067] Specifically, from the standpoint of the avoidance of the influence of charge-up damage or arcing damage, it can be said that the outer diameter of the focus ring 5 is preferably set to be in the range of from 412 mm to 420 mm when the diameter of the wafer W is 12 inches if the power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power supply 10 is not less than 2.8 W/cm² and less than 3.9 W/cm².

[0068] From the standpoint of the avoidance of the influence of occurrence of charge-up damage and arcing damage, it can be said that the outer diameter of the focus ring 5 is preferably set to be in the range of from 412 mm to 420 mm when the diameter of the wafer W is 12 inches if the power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power supply 10 is not less than 2.8 W/cm² and less than 3.9 W/cm².

[0069] From the standpoint of the avoidance of the influence of occurrence of arcing-up damage regardless of the presence of occurrence of charge-up damage, it can be said that the outer diameter of the focus ring 5 is preferably set so as to exceed 412 mm and to be 420 mm or less when the diameter of the wafer W is 12 inches if the power density of the high-frequency field supplied to the surface of the wafer W by the high-frequency power supply 10 is in the range of from 2.8 W/cm² to 3.9 W/cm².

[0070] As described above, according to the present invention, the conductive or insulating focus ring is provided around the object to be processed, on the first electrode, and the ratio of the outside of the focus ring to the diameter of the object is set to be in the range of from about 1.3 to about 1.4. Therefore, it is possible to carry out a uniform plasma processing in the plane of the object to be processed, and it is possible to avoid the occurrence of charge-up damage or arcing damage.

[0071] While the present invention has been disclosed in terms of the preferred embodiment in order to facilitate better understanding thereof, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible embodiments and modification to the shown embodiments which can be embodied without departing from the principle of the invention as set forth in the appended claims. 

What is claimed is:
 1. A plasma processing system comprising: a chamber capable of being held in vacuum; a pair of electrodes which face each other in said chamber, said pair of electrodes comprising a first electrode for supporting thereon a substrate to be processed, and a second electrode facing the first electrode; electric field forming means for forming a high-frequency field having a predetermined power density between said pair of electrodes; process gas supply means for supplying a process gas into said chamber; magnetic field forming means, provided around said chamber, for forming a magnetic field around a processing space which is formed between said pair of electrodes; and a conductive or insulating focus ring which is provided around said substrate on said first electrode, wherein the ratio of the outer diameter of said focus ring to the diameter of said substrate is set to be in the range of from about 1.3 to about 1.4.
 2. A plasma processing system as set forth in claim 1, wherein the outer diameter of said focus ring is set to be in the range of from 275 mm to 280 mm when the diameter of said substrate is 203 mm (8 inches) if the power density of said high-frequency field applied to said substrate is in the range of from 2.8 W/cm² to 3.9 W/cm².
 3. A plasma processing system as set forth in claim 2, wherein the outer diameter of said focus ring is set to be greater than 275 mm and not greater than 280 mm when the diameter of said substrate is 203 mm (8 inches) if the power density of said high-frequency field applied to said substrate is in the range of from 2.8 W/cm² to 3.9 W/cm².
 4. A plasma processing system as set forth in claim 2, wherein the outer diameter of said focus ring is set to be in the range of from 275 mm to 280 mm when the diameter of said substrate is 203 mm (8 inches) if the power density of said high-frequency field applied to said substrate is not less than 2.8 W/cm² and less than 3.9 W/cm².
 5. A plasma processing system as set forth in claim 1, wherein the outer diameter of said focus ring is set to be in the range of from 412 mm to 420 mm when the diameter of said substrate is 305 mm (12 inches) if the power density of said high-frequency field applied to said substrate is in the range of from 2.8 W/cm² to 3.9 W/cm².
 6. A plasma processing system as set forth in claim 5, wherein the outer diameter of said focus ring is set to be greater than 412 mm and not greater than 420 mm when the diameter of said substrate is 305 mm (12 inches) if the power density of said high-frequency field applied to said substrate is in the range of from 2.8 W/cm² to 3.9 W/cm².
 7. A plasma processing system as set forth in claim 5, wherein the outer diameter of said focus ring is set to be in the range of from 412 mm to 420 mm when the diameter of said substrate is 305 mm (12 inches) if the power density of said high-frequency field applied to said substrate is not less than 2.8 W/cm² and less than 3.9 W/cm².
 8. A plasma processing system as set forth in claim 1, wherein the outer diameter of said focus ring is set to be in the range of from 275 mm to 280 mm when the diameter of said substrate is 203 mm (8 inches), and in the range of from 412 mm to 420 mm when the diameter of said substrate is 305 mm (12 inches), if the power density of said high-frequency field applied to said substrate is 2.8 W/cm².
 9. A plasma processing system as set forth in claim 1, wherein the outer diameter of said focus ring is set to be greater than 275 mm and not greater than 280 mm when the diameter of said substrate is 203 mm (8 inches), and is set to be greater than 412 mm and not greater than 420 mm when the diameter of said substrate is 305 mm (12 inches), if the power density of said high-frequency field applied to said substrate is 3.9 W/cm². 